Seat back



FIG. 1 is a front view of a seat back showing my design;

FIG. 2 is a back view of a seat back;

FIG. 3 is a left side view of a seat back;

FIG. 4 is a right side view of a seat back;

FIG. 5 is a top plan view of a seat back;

FIG. 6 is a bottom plan view of a seat back; and,

FIG. 7 is a perspective view of a seat back. 

CLAIM The ornamental design for seat back, as shown and described. 